Purpose: :
To determine the time course of the concentration ofbimatoprost and its acid in the aqeous humor in humans afteradministration of a single drop.

Methods: :
In a single masked randomized clinical trial 31 subjectsscheduled for routine cataract surgery received a single dropof bimatoprost 2 hours (n=15), 4 hours (n=8) and 12 hours (n=8)prior to surgery. None of the patients used any other eye dropsor had any ocular abnormality other than cataract. Aqueous humorsamples were drawn and deep frozen to –70°C. The sampleswere examined by an independent lab using HPLC–tandemmass spectrometry. The lower limit of quantification was 0.5ng/mlfor bimatoprost and its acid.

Conclusions: :
After a single drop of bimatoprost bimatoprostand its acid were detectable in the aqeous humor. The concentrationof bimatoprost acid was higher than the concentration of bimatoprost.The highest concentrations of bimatoprost and its acid werepresent 2 hours after administration.